This proposal addresses the NIA Program (PA-97-097), "The Impact of Immune Senescence and Maturation on Vaccine Responsiveness in the Elderly" and describes a strategy to advance the basic science of influenza learned from studies in the aged mouse model which will be applied to a very high-risk population of older adults with congestive heart failure (CHF). The innovation in this proposal has been the development of a simple laboratory measure of cytotoxic T-lymphocyte (CTL) activity using an ex vivo assay of granzyme B (Grz B). This translational research will characterize the protective immunologic response to influenza vaccination, define the defective T-cell mechanism that increases risk for influenza in older adults, and determine individual risk based on clinical markers of disease severity in CHF. CHF provides a model for studying the significant added risk of serious influenza illness to that related to advancing age. In the process, important clinical indicators and laboratory measures of influenza risk will identify older people with a high risk for serious influenza illness. The general hypothesis is that Iow levels of Grz B predict high risk for influenza illness and are associated with a dysregulation of cytokine production in older adults. To explore this hypothesis, vaccinated healthy older adults and older adults with CHF will be studied to determine the: 1) association between antibody, cytokine and Grz B levels and the development of influenza illness, 2) mechanism underlying poor Grz B responses to influenza vaccination with advancing age and CHF, and 3) relationship between functional performance and antibody, cytokine and Grz B levels Aim (1) will be accomplished by measuring antibody, cytokine and Grz B levels before and after influenza vaccination in different risk groups for influenza. From these results, the principal investigator will test a threshold level of Grz B for its ability to predict risk for influenza-related illness in older people with CHF. The components of a "protective" T-cell response to vaccination will be defined. Aim (2) will be accomplished by measuring age and CHF-related changes in cytokine and Grz B levels and the number virus-specific T-cells in different T-cell subsets. Aim (3) will be accomplished by comparing cytokine and Grz B levels in virus-stimulated PBMC, to clinical indicators of CHF severity as a potential marker of "immunologic frailty" for complications of influenza. By comparing these immune responses to influenza vaccination in healthy young and older adults and older adults with CHF, the mechanism that leads to decreased efficacy of current influenza vaccines will be identified. The goal is to define an immunologic test that measures influenza risk, a measure critical to future vaccine development and targeted prophylaxis in older adults.